There is an increasing interest on the use of hydrocarbon components of biological origin from renewable sources in fuels to replace the fossil starting materials. The use thereof is highly desirable for environmental reasons. There is a lot of literature relating to production of fuel composition from biological starting materials like vegetable oils, such as tall oil.
US 2004/0230085 A1 discloses a process for producing hydrocarbon components from wood-based tall oil by a two-step procedure in which a fatty acid fraction of tall oil (TOFA) is subjected to a hydrodeoxygenation step to hydrogenate TOFA in the presence of a desulphurization catalyst and then to an isomerization step to branch the hydrocarbon chain. The products obtained from the isomerization are predominantly i-paraffins which are suitable for use as components in diesel fuels. The hydrocarbon chain lengths suitable for diesel components are typically in the range of C9-C20.
US 2009/0020089 A1 discloses a fuel composition comprising at least a tetramethylcyclohexane and optionally an aromatic isoprenoid compound, and a monocyclic and acyclic hydrocarbon component. The fuel composition can be of petrol fuel grade, for example. The tetramethylcyclohexane is produced by hydrogenation of pinene in the presence of a hydrogenation catalyst. Pinene and the starting materials for the optional components included in the fuel composition are produced by microbiological methods using a host cell.
Tall oil is retrieved from the kraft pulping process of coniferous wood as a by-product. From the same process, also crude turpentine is extracted as a by-product. Chemical compositions of said substances differ from each other to a significant extent. Tall oil is mainly composed of fatty acids and resin acids with a chain length varying between C12 to C18, and fused ring systems as abietic acids and sitosterols, while the crude turpentine comprises an oil mixture of terpenes derived from pitch. Terpenes are a wide range of volatile hydrocarbons having a chemical formula of C10H16, including typically unsaturated mono- and bicyclic hydrocarbons. Crude turpentine, which contains terpenes, is formed in the kraft pulping process is generally referred to as crude sulphate turpentine (CST). The main terpene components included in the CST are α-pinene, β-pinene and and Δ-3-carene. The major component is typically α-pinene.

The unsaturated bicyclic terpenes included in the turpentine, having the formulas given above, are too reactive as such for use as fuel components. Also, the high sulphur content of the turpentine prevents using it for fuel application.
Processes for converting terpenes to cymenes are previously known. In these processes, different types of catalysts are used for the conversion. For example, alkali metal carbonate catalysts, catalysts comprising noble metals or rare earth metals on a zeolite support and a palladium catalyst supported on activated carbon or alumina have been used.
CST comprising a large amount of terpene isomers also contains a relatively high amount of sulphur, up to 6%, as a contaminant. In order to be able to utilize the CST for further applications sulphur has to be removed from it. In EP 0267833 A1 sulphur is removed from the terpenes included in the crude turpentine through hydrogenation in the presence of a catalyst of cobalt and molybdenum oxides on an inorganic support. It is desired that any chemical transformation of the terpenes is avoided during the hydrodesulphurization procedure.
At present, the crude sulphate turpentine is processed for use as a solvent or odorants in pharmaceutical and cosmetic industry. However, a wide range of utilization of the turpentine is restricted because of the high level of sulphur, and no cost efficient processes for desulphurization and refining the turpentine are now present. Accordingly, a large amount of the crude sulphate turpentine is now burned without further processing.